Dose Setting Mechanism for an Injection Device Capable of Presetting a Maximum Dose

ABSTRACT

A dose setting mechanism for an injection device having a rotatably operated dose setting member. Has a presetting member being operable to limit the maximum dose settable by the dose setting member. A first stopping member is operatively connected to the presetting member, and the position of the first stopping member indicates the preset maximum dose. The first stopping member is adapted to rotatably engage with a second stopping member when the preset maximum dose has been set, thereby preventing setting of a further dose. The first and/or the second stopping member is/are movable along with the dose setting member, the first and second stopping members thereby being moved into engagement when a dose is set. Thereby a dose can be preset and the preset dose can easily be repeatedly set while ensuring an accurate dosage. Helps persons being visually impaired or having poor dexterity in setting a correct and accurate dose. Further, an injection device with a dose setting mechanism, particularly for self-injection of e.g. insulin.

FIELD OF THE INVENTION

The present invention relates to a dose setting mechanism for aninjection device, preferably of the kind being suitable for repetitiveself-injection of medication, e.g. of insulin or growth hormone, thedose setting mechanism making it easy for a user to set a predetermineddose. Furthermore, the present invention relates to an injection devicehaving such a dose setting mechanism.

BACKGROUND OF THE INVENTION

When drugs are to be injected into the human body, it is often essentialthat the dose to be injected is set with high precision, as a too highor too low dose can have undesired consequences. However, for personsbeing visually impaired or having poor dexterity it may be difficult toset the desired dose. Accordingly, it is desirable to provide aninjection device with a preset mechanism which aids such persons in theprocess of setting a dose.

One such device is described in U.S. Pat. No. 6,228,067 disclosing aninjection device having a movable expressing member for expressing aninjection fluid from a fluid container. An actuating member is used fordisplacing the expressing member. Between the actuating member and theexpressing member, a position-dependent connecting device is provided,which is disabled in a distal end position of the actuating member andis enabled in a position range adjacent to the distal end position ofthe actuating member, including a proximal end position. Thereby aninjection device is obtained which is adapted to permit a patient torepeatedly administer the same constant injection dose. The preset doseis set by pulling the actuating member out until this movement isstopped by means of the connecting device. Subsequently the set dose isinjected by pressing the actuating member. Thus, the preset mechanismhas been applied to an injection device in which the dose setting aswell as the injection is performed by means of linear movements. This isa disadvantage because setting and/or injecting a dose of oneinternational unit corresponds to a very small movement of the actuatingmember, and it is therefore difficult to set and/or inject an accuratedose. Accordingly, it is also difficult to set the preset doseaccurately and thereby to ensure subsequent accurate dosage. This isparticularly disadvantageous because a too high or too low preset dosewill result in a too high or too low dose being set each time the presetdose is set, and the accumulated dose over a longer period in time willtherefore deviate substantially from what was intended.

U.S. Pat. No. 5,308,340 discloses a multiple dose injection pencomprising a follower which can be adjusted to any position alongthreads adapted to engage with internal threads of a dose knob. Theprinciple function of the follower is to set a maximum allowable dosewhere the syringe is going to be used by persons who may have difficultyremembering the proper dosage. The follower limits the axial movement ofthe dose knob during setting of a dose, since the follower will abut acollar of the dose knob when the maximum dosage has been set. Thefollower and the collar are moved linearly into abutment.

EP 0 937 471 discloses a medication delivery pen having a repeat-dosefeature that limits motion of the dose control mechanism using anadjustable repeat-dose stop on the dose knob. The pen comprises anadjustable dose stop which prevents axial movement of the dose knobbeyond a set desired dose. When the desired dose has been set, aproximal face of the dose stop comes into contact with a distal face ona clicker, thereby preventing further axial movement of the dose knob.The faces are moved linearly into contact.

SUMMARY OF THE INVENTION

It is, thus, an object of the present invention to provide a dosesetting mechanism having a preset mechanism which can be set moreaccurately than prior art preset mechanisms.

It is a further object of the present invention to provide a presetmechanism for a dose setting mechanism in which the dose can be set inan accurate manner.

It is an even further object of the present invention to provide aninjection device in which a desired dose may easily and accurately berepeatedly set.

According to a first aspect of the present invention the above and otherobjects are fulfilled by providing a dose setting mechanism for aninjection device, the dose setting mechanism comprising:

-   -   a dose setting member being rotatably operable by a user to set        a desired dose,    -   a presetting member being operable to limit the maximum dose        settable by the dose setting member,    -   a first stopping member being operatively connected to the        presetting member in such a manner that the position of the        first stopping member is changed when the presetting member is        operated, the position of the first stopping member thereby        being indicative of the preset maximum settable dose,    -   a second stopping member being adapted to engage with the first        stopping member in such a way that when the first stopping        member and the second stopping member engage, the dose setting        member can not be operated to set a further dose,        wherein the first and/or the second stopping member is/are        movable along with the dose setting member during setting of a        dose, said movement causing the first and the second stopping        member to perform a rotational movement relatively to each        other, said relative rotational movement causing the first and        the second stopping member to engage when the maximum settable        dose has been set, thereby preventing further setting of a dose.

In the present context the term ‘dose setting mechanism’ should beinterpreted to mean a part of an injection device which is used forsetting a dose to be injected by means of the injection device. Theinjection device is preferably of the kind being suitable for repetitiveself-injections of medication, such as insulin or growth hormone. Theinjection device is of the kind where the dose setting as well as theinjection is performed by means of rotating movements. In such injectiondevices the dose setting as well as the injection of the set dose ismuch more accurate than dose setting and injection in injection deviceswhere these functions are performed linearly. This is because therotational movements provide a longer path to be traveled by theinvolved components when setting or injecting a dose of oneinternational unit. In addition to the rotational movement, the dosesetting member may perform a translational movement, the resultingmovement of the dose setting member thereby being a spiral movement.

The dose setting member is a part of the dose setting mechanism whichcan be rotatably operated by the user in order to set a desired dose.The dose setting member could, thus, be or comprise a rotatable doseknob or another mechanism which is normally used for this purpose ininjection devices of the kind mentioned above.

The presetting member is operable to limit the maximum dose settable.Thus, the presetting member can be operated so as to set a ‘maximumdose’. When a maximum dose has been set by means of the presettingmember, this dose may be set repeatedly by the user merely by operatingthe dose setting member to the maximum dose each time a dose is to beset. This makes it easier for persons being visually impaired or havingpoor dexterity, or for children, to set a correct dose. Furthermore, thepreset limit can easily be changed in case the dose needs to be changed.

The first stopping member is operatively connected to the presettingmember. Thus, when the presetting member is operated by a user, thefirst stopping member is moved accordingly, i.e. the position of thefirst stopping member is changed in accordance with the presetting ofthe maximum dose settable. Thus, the position of the first stoppingmember is indicative of the preset maximum dose. The first stoppingmember may be or form part of the presetting member. Alternatively, thefirst stopping member may be connected to the presetting member in amechanical or electronical manner, or in any other suitable manner aslong as the operation of the presetting member causes the first stoppingmember to move.

When a dose is set by rotating the dose setting member, the first and/orsecond stopping member is moved along with the dose setting member. Thismovement causes the distance between the first stopping member and thesecond stopping member to decrease in such a way that when the positionof the first stopping member coincides with the position of the secondstopping member, the first and second stopping members thereby engagingeach other, the maximum dose settable has been set. The engagement ofthe first and second stopping members thereby has the effect that afurther dose can not be set, i.e. it is not possible to set a dose whichexceeds the preset maximum dose. It is of no importance whether it isthe first stopping member, the second stopping member or both whichis/are moved along with the dose setting member as long as the movementcauses a decrease in the distance between the first stopping member andthe second stopping member as described above.

In the present context the term ‘movable along with the dose settingmember’ should not be interpreted narrowly as ‘performing the samemovement as the dose setting member’. Rather, the stopping member(s)is/are caused to move when the dose setting member is rotated to set adose, and the kind of movement or the direction of movement need not bethe same as the physical movement of the dose setting member. What isimportant is, that the first stopping member and the second stoppingmember are caused to perform a rotational movement relatively to eachother when the dose setting member is rotated to set a dose, and thatthis relative rotational movement causes the distance between the firststopping member and the second stopping member to decrease in such a waythat when the preset maximum dose has been set by the dose settingmember, the first stopping member and the second stopping member engage,thereby preventing setting of a further dose. Thus, during the settingof a dose the distance between the first stopping member and the secondstopping member in effect indicates how much further dose can be setbefore the preset maximum dose has been set.

It is an advantage that the first and second stopping member are movedinto engagement by means of a relative rotational movement, because therelative rotational movement provides a more accurate definition of thepoint where the maximum settable dose has been reached, than it is thecase for a relative linear movement.

In the present context the term ‘distance’ should be broadlyinterpreted. Thus, the distance could, e.g., be an angular and/or anaxial distance.

Thus, according to the present invention a preset mechanism has beenapplied to a device in which the dose setting as well as the injectionis performed by means of rotating movements, the dosage thereby beingprovided in a very accurate manner. Accordingly, the dose settingmechanism of the present invention combines an accurate dose settingwith a preset mechanism, thereby providing accurate dosage, also forpersons being visually impaired or having poor dexterity.

The first and/or the second stopping member may rotate along with thedose setting member during setting of a dose. Alternatively oradditionally, the first and/or the second stopping member may perform atranslational movement, e.g. along a longitudinal axis of the injectiondevice.

In one embodiment the first stopping member is movable along with thedose setting member during setting of a dose, the second stopping memberbeing at least substantially fixed relatively to a housing of theinjection device. In this embodiment the second stopping member remainsat least substantially fixed relatively to the housing while the firststopping member is movable along with the presetting member duringpresetting of the maximum dose as well as along with the dose settingmember during setting of a dose. Alternatively, the first stoppingmember may remain at least substantially fixed relatively to the housingduring the setting of a dose in which case only the second stoppingmember is moved along with the dose setting member. Alternatively, thefirst stopping member as well as the second stopping member may bemovable along with the dose setting member during setting of a dose.This has already been described above.

The first stopping member and the second stopping member may eachcomprise at least one stopping surface, the stopping surfaces of thefirst and second stopping members being adapted to abut each other whenthe maximum settable dose has been set, thereby preventing furtherrelative rotational movement between the first and the second stoppingmember. In this embodiment the first and/or the second stopping memberperform(s) a rotational movement during setting of a dose. At least oneof the first and second stopping members may further perform atranslational movement, the resulting movement of at least one of thestopping members thereby being a spiral movement. In any event themovement is performed until the stopping surfaces abut, therebypreventing further mutual rotational movement. This, in turn, preventsfurther setting of a dose.

The first stopping member and the second stopping member may eachcomprise a plurality of teeth, the number of teeth on each stoppingmember corresponding to the number of unit doses being set when the dosesetting member is rotated through one revolution. In this embodiment aspiral movement of at least one of the first and second stopping membersduring setting of a dose is necessary in order to allow relativerotation during setting of a dose up until the maximum dose, and inorder to prevent further relative rotation when the maximum dose hasbeen set. When the number of teeth on each stopping member correspondsto the number of unit doses per revolution, it is ensured that settingof a further dose is prevented exactly when the preset dose has beenset, i.e. it is not possible to set a dose which is a few units higherthan the preset dose. This even further improves the accuracy of thepresetting mechanism.

According to a second aspect of the present invention the above andother objects are fulfilled by providing an injection device comprisinga dose setting mechanism according to the first aspect of the presentinvention. The injection device may be of the kind which is suitable forrepetitive self-injection of medication, such as insulin or growthhormone. Preferably, the injection device has an elongated shape, i.e.it is preferably of a pen-shaped type.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to theaccompanying drawings, in which:

FIG. 1 is a perspective view of an injection device with a dose settingmechanism according to an embodiment of the present invention,

FIG. 2 is a side view of the injection device of FIG. 1 with partsbroken away,

FIG. 3 is a cross sectional view of the injection device of FIG. 1,where the presetting member has been set to a maximum dose,

FIG. 4 is a cross sectional view of the injection device of FIG. 1 wherea maximum dose has been set by means of the dose setting mechanism,

FIG. 5 is a cross sectional view of the injection device of FIG. 1,where the presetting member has been set to a maximum dose of 0 units,and

FIG. 6 is an exploded view of the injection device of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an injection device 1 having a dosesetting mechanism according to an embodiment of the present invention.The dose setting mechanism is operated by means of a dose setting member2. When a dose is set the dose setting member 2 is rotated, therebycausing a scale drum 3 to be rotated as well. The rotational movementalso results in an axial movement of the dose setting member 2 and thescale drum 3 in an outward direction. The scale drum 3 is visiblethrough a window 4 in a housing 5 of the injection device 1. Thereby itis possible for a user to read the set dose by means of numbers writtenon the scale drum 3. The injection device 1 further comprises acompartment 6 adapted to accommodate a cartridge containing a fluid tobe injected by means of the injection device 1. At the end 7 positionedopposite the dose setting member 2 it is possible to attach an injectionneedle. Finally, the dose setting mechanism comprises a presettingmember 8 which is rotatable in order to preset a desired maximum dose.

FIG. 2 is a side view of the injection device 1 of FIG. 1. Part of thehousing 5 has been broken away, thereby revealing the position of thescale drum 3 inside the housing 5. The dose setting member 2 ispositioned adjacent to the presetting member 8, i.e. a dose has not beenset.

FIG. 3 is a cross sectional view of the injection device 1 of FIG. 1.However, part of the scale drum 3 is still visible. In FIG. 3 a firststopping member 9 is shown. The first stopping member 9 is operativelyconnected to the presetting member 8 by means of a thread 10 on thefirst stopping member 9 and a corresponding inner thread 11 on thepresetting member 8. Thus, when the presetting member 8 is rotated thefirst stopping member 9 performs a spiral movement, and the resultingposition of the first stopping member 9 will be indicative of the presetmaximum settable dose. In FIG. 3 the presetting member 8 has been set toa non-zero maximum dose.

FIG. 4 is also a cross sectional view of the injection device 1 ofFIG. 1. In FIG. 4 a second stopping member 12 in the form of a toothpresent on the housing 5 is visible. The first stopping member 9 abutsthe second stopping member 12, thereby indicating that the dose set isthe maximum settable dose, i.e. it is not possible to set a furtherdose.

FIG. 5 is also a cross sectional view of the injection device 1 ofFIG. 1. In this case the presetting member 8 has been preset to amaximum settable dose of 0 units. This can be seen because the firststopping member 9 and the second stopping member 12 abut each other, andthe dose setting member 2 is in the ‘zero position’, i.e. it has notbeen dialled away from the presetting member 8. Such a setting may,e.g., be used in case it is desired to prevent that a dose isaccidentally set.

FIG. 6 is an exploded view of the injection device 1 of FIG. 1. In thisFigure the shapes of the various parts are clearly visible.

It should be noted that, for the sake of clarity, only one tooth isshown on first stopping member 9 and on the second stopping member 12.However, it should be understood that additional teeth may be present onthe respective stopping members 9, 12, preferably the number of teeth oneach stopping member 9, 12 corresponds to the number of unit doses beingset when the dose setting member 2 is rotated through one revolution.

The stopping member 9 comprises an inner key (not shown) which engagesan outer groove 13 on the scale drum 3. During setting of a maximumsettable dose, the stopping member 9 is thereby moved along this outergroove 13 by means of a key-groove connection.

The injection device 1 shown in FIGS. 1-6 is preferably operated in thefollowing manner. When it is desired to preset a maximum settable dose,the dose setting mechanism is initially operated to set this dose byrotating the dose setting member 2 in a manner normal for this kind ofinjection device 1. Once the desired dose is set the presetting member 8is rotated until the first stopping member 9 (connected to thepresetting member 8) abuts the second stopping member 12 (fixed to thehousing 5). Thereby the presetting member 8 has been set to the desiredmaximum settable dose. When the set dose is subsequently injected bypressing the dose setting member 2 (and along with it the scale drum 3)back towards the housing 5, the first stopping member 9 will be forcedto perform a translational movement away from the second stopping member12. Thereby the first stopping member 9 and the second stopping member12 no longer abut each other. The distance traveled by the firststopping member 9 is indicative of the dose being injected, i.e. themaximum settable dose. Accordingly, the resulting position of the firststopping member 9 is indicative of the preset maximum dose. The nexttime a dose is to be set, the dose setting member 2 is rotated in theusual manner. The first stopping member 9 will be forced to rotate andto translate in a direction towards the second stopping member 12.Thereby the dose setting member 2 can only be rotated until the presetmaximum dose has been set, because when this is the case, the firststopping member 9 will again be in the position where it abuts thesecond stopping member 12, and a further dose can not be set. Therebythe preset maximum dose can be repeatedly set and injected until it isdesired to change the dose. Then a new preset value is simply selectedas described above.

1. A dose setting mechanism for an injection device, the dose settingmechanism comprising: a dose setting member being rotatably operable bya user to set a desired dose, a presetting member being operable tolimit the maximum dose settable by the dose setting member, a firststopping member being operatively connected to the presetting member insuch a manner that a position of the first stopping member is changedwhen the presetting member is operated, the position of the firststopping member thereby being indicative of the preset maximum settabledose, a second stopping member being adapted to engage with the firststopping member in such a way that when the first stopping member andthe second stopping member engage, the dose setting member cannot beoperated to set a further dose, wherein the first and/or the secondstopping member is/are movable along with the dose setting member duringsetting of a dose, said movement causing the first and the secondstopping member to perform a rotational movement relatively to eachother, said relative rotational movement causing the first and thesecond stopping member to engage when the maximum settable dose has beenset, thereby preventing further setting of a dose.
 2. The dose settingmechanism according to claim 1, wherein the first and/or the secondstopping member rotate(s) along with the dose setting member duringsetting of a dose.
 3. The dose setting mechanism according to claim 1,wherein the first stopping member is movable along with the dose settingmember during setting of a dose, the second stopping member being atleast substantially fixed relatively to a housing of the injectiondevice.
 4. The dose setting mechanism according to claim 1, wherein thefirst stopping member and the second stopping member each comprises atleast one stopping surface, the stopping surfaces of the first andsecond stopping members being adapted to abut each other when themaximum settable dose has been set, thereby preventing further relativerotational movement between the first and the second stopping member. 5.The dose setting mechanism according to claim 4, wherein the firststopping member and the second stopping member each comprises aplurality of teeth, the number of teeth on each stopping membercorresponding to the number of unit doses being set when the dosesetting member is rotated through one revolution.
 6. An injection devicecomprising a dose setting mechanism according to claim
 1. 7. The dosesetting mechanism according to claim 2, wherein the first stoppingmember is movable along with the dose setting member during setting of adose, the second stopping member being at least substantially fixedrelatively to a housing of the injection device.
 8. The dose settingmechanism according to claim 2, wherein the first stopping member andthe second stopping member each comprises at least one stopping surface,the stopping surfaces of the first and second stopping members beingadapted to abut each other when the maximum settable dose has been set,thereby preventing further relative rotational movement between thefirst and the second stopping member.
 9. The dose setting mechanismaccording to claim 3, wherein the first stopping member and the secondstopping member each comprises at least one stopping surface, thestopping surfaces of the first and second stopping members being adaptedto abut each other when the maximum settable dose has been set, therebypreventing further relative rotational movement between the first andthe second stopping member.
 10. The dose setting mechanism according toclaim 7, wherein the first stopping member and the second stoppingmember each comprises at least one stopping surface, the stoppingsurfaces of the first and second stopping members being adapted to abuteach other when the maximum settable dose has been set, therebypreventing further relative rotational movement between the first andthe second stopping member.
 11. An injection device comprising a dosesetting mechanism according to claim
 2. 12. An injection devicecomprising a dose setting mechanism according to claim
 3. 13. Aninjection device comprising a dose setting mechanism according to claim4.
 14. An injection device comprising a dose setting mechanism accordingto claim
 7. 15. An injection device comprising a dose setting mechanismaccording to claim
 8. 16. An injection device comprising a dose settingmechanism according to claim
 9. 17. An injection device comprising adose setting mechanism according to claim
 10. 18. An injection devicecomprising a dose setting mechanism according to claim 5.